1. Field of the Invention
The present invention relates to novel methods and systems for controlling the concentration of a component in a composition. The invention also relates to novel semiconductor processing methods and systems. The invention has particular applicability to the semiconductor manufacturing industry for online monitoring and control of the concentration of a corrosion inhibitor in a process chemical.
2. Description of the Related Art
Chemical mechanical planarization (CMP), also referred to as chemical mechanical polishing, and pre- and post-CMP storage and cleaning processes are commonly used in the manufacture of integrated circuits (ICs). To avoid corrosion of exposed metal during a metal CMP process, for example, for the planarization of copper-containing layers such as copper and copper-alloy layers, corrosion inhibitors such as benzotriazole, hydroquinone, tolyltriazole, imidazole, triazole, benzothiazole, mercaptobenzotriazole, gallic acid, pyragallol, catechol, recorsinol, etc., can be employed with the CMP slurry. In the CMP process, the corrosion inhibitor, typically in the form of a complex with the metal, passivates the metal surface of the wafer against chemical etching and allows uniform removal of the oxidized layer by mechanical action. The corrosion inhibitor complex also prevents the diffusion of oxygen into the wafer during subsequent, post-CMP cleaning operations. Liquid chemicals containing a corrosion inhibitor can also be used in a bath for storage or cleaning purposes before and/or after the CMP process to prevent corrosion of the metal surface.
It is desirable to maintain a known, constant concentration of the corrosion inhibitor in the CMP process and pre- and post-treatment baths in order to provide a manufacturable process. A decreased corrosion inhibitor level increases the likelihood of metal corrosion, whereas an increased concentration can result in corrosion inhibitor residue remaining on the wafer surface. These effects can result in a significant decrease in product yield. While off-line methods for measurement of the concentration of the corrosion inhibitors exist, such methods do not provide real-time feedback and control of the process.
Accordingly, there is a need in the art for methods and apparatuses for controlling the concentration of components such as a corrosion inhibitor in a CMP chemical and in pre- and post-CMP storage/treatment chemicals, which can provide real time, accurate process control in an easy and robust manner.
According to a first aspect of the invention, provided is method of controlling the concentration of a component in a composition, which involves: providing a composition containing a liquid portion, wherein the liquid portion comprises a component to be monitored; performing an absorption spectroscopy measurement on a sample of the composition; and controlling the concentration of the component in the composition based on the absorption spectroscopy measurement using a feedback control loop.
The component to be monitored can be, for example, a corrosion inhibitor, such as benzotriazole, tolyltriazole, imidazole, triazole, benzothiazole, mercaptobenzotriazole, hydroquinone, gallic acid, pyragallol, catechol, recorsinol, or a combination thereof. The concentration of the component in the composition can be controlled by adjustment of the amount of the component introduced into the CMP apparatus or by adjustment of the amount of a diluent introduced into the CMP apparatus. The absorption spectroscopy measurement can be, for example, a UV/visible light spectroscopy measurement.
According to a further aspect of the invention, provided is a semiconductor processing method. The method involves: contacting a semiconductor wafer with a solution containing a component to be monitored; controlling the concentration of the component by a method involving: performing an absorption spectroscopy measurement on a sample of the solution; and controlling the concentration of the component in the solution based on the absorption spectroscopy measurement using a feedback control loop.
In accordance with a further aspect of the invention, a system for controlling the concentration of a component in a composition is provided. The system includes: a source of a composition which has a liquid portion, wherein the liquid portion contains a component to be monitored; an absorption spectroscopy measurement apparatus for measuring the concentration of the component in a sample of the composition; and feedback control means for controlling the concentration of the component in the composition based on the absorption spectroscopy measurement.
The absorption spectroscopy system can have a plurality of measurement cells, as well as means for directing a sample to be measured to an appropriate measurement cell based on the amount of the component to be monitored.
In accordance with a further aspect of the invention, a semiconductor processing system is provided. The system includes: a chemical bath tank containing a solution for treating a semiconductor substrate; one or more conduits for introducing process materials into the chemical bath, the process materials containing a component to be monitored; an absorption spectroscopy measurement apparatus for measuring the concentration of the component in a sample of the solution; and feedback control means for controlling the concentration of the component in the solution based on the absorption spectroscopy measurement.
The methods and systems of the invention can effectively provide real-time, accurate process control, providing fast response time. The concentration of chemical species, which are otherwise not easily measurable using conventional techniques, can easily and accurately be determined.